Note: Descriptions are shown in the official language in which they were submitted.
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AERODYNAMICALLY ENHANCED FUEL NOZZLE
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
The present invention relates to gas turbine engine fuel nozzles and, more
particularly, to
such fuel nozzles having pilot fuel injector tips containing pilot fuel
nozzles.
DESCRIPTION OF RELATED ART
Aircraft gas turbine engine staged combustion systems have been developed to
limit the
production of undesirable combustion product components such as oxides of
nitrogen
(NOx), unburned hydrocarbons (HC), and carbon monoxide (CO) particularly in
the
vicinity of airports, where they contribute to urban photochemical smog
problems. Gas
turbine engines also are designed to be fuel efficient and have a low cost of
operation.
Other factors that influence combustor design are the desires of users of gas
turbine
engines for efficient, low cost operation, which translates into a need for
reduced fuel
consumption while at the same time maintaining or even increasing engine
output. As a
consequence, important design criteria for aircraft gas turbine engine
combustion systems
include provisions for high combustion temperatures, in order to provide high
thermal
efficiency under a variety of engine operating conditions, as well as
minimizing
undesirable combustion conditions that contribute to the emission of
particulates, and to
the emission of undesirable gases, and to the emission of combustion products
that are
precursors to the formation of photochemical smog.
One mixer design that has been utilized is known as a twin annular premixing
swirler
(TAPS), which is disclosed in the following U.S. Patent Nos. 6,354,072;
6,363,726;
6,367,262; 6,381,964; 6,389,815; 6,418,726; 6,453,660; 6,484,489; and,
6,865,889. It
will be understood that the TAPS mixer assembly includes a pilot mixer which
is
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supplied with fuel during the entire engine operating cycle and a main mixer
which is
supplied with fuel only during increased power conditions of the engine
operating cycle.
While improvements in the main mixer of the assembly during high power
conditions
(i.e., take-off and climb) are disclosed in patent applications having Serial
Nos.
11/188,596, 11/188,598, and 11/188,470, modification of the pilot mixer is
desired to
improve operability across other portions of the engine's operating envelope
(i.e., idle,
approach and cruise) while maintaining combustion efficiency. To this end and
in order
to provide increased functionality and flexibility, the pilot mixer in a TAPS
type mixer
assembly has been developed and is disclosed in U.S. Patent No. 7,762,073,
entitled
"Pilot Mixer For Mixer Assembly Of A Gas Turbine Engine Combustor Having A
Primary Fuel Injector And A Plurality Of Secondary Fuel Injection Ports" which
issued
July 27, 2010. This patent is owned by the assignee of the present application
and hereby
incorporated by reference.
United States Patent Application No. Serial No. 12/424,612 (PUBLICATION NUMBER
20100263382), filed April 16, 2009, entitled "DUAL ORIFICE PILOT FUEL
INJECTOR" discloses a fuel nozzle having first second pilot fuel nozzles
designed to
improve sub-idle efficiency, reduced circumferential exhaust gas temperature
(EGT)
variation while maintaining a low susceptibility to coking of the fuel
injectors. This
patent application is owned by the assignee of the present application and
hereby
incorporated by reference.
It is highly desirable to improve the operating efficiency of fuel nozzles.
More
particularly, it is highly desirable to optimize pilot air flow rate, and
strengthen pilot inner
swirl number. It is also highly desirable to minimize flow obstruction
(leading to flow
asymmetry) and maximize pilot air flow-rate within a given fuel nozzle
envelope.
SUMMARY OF THE INVENTION
A gas turbine engine fuel nozzle assembly includes a pilot fuel injector tip
substantially
centered about a centerline axis in an annular pilot inlet to a pilot mixer
and a cross over
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arm extending radially across the annular pilot inlet to the pilot fuel
injector tip. The
cross over arm includes an arm fairing surrounding at least one fuel transfer
tube to the
pilot fuel injector tip and a pilot nose cap located at an upstream end of the
pilot fuel
injector tip. At least one of the cross over arm and the pilot nose cap
includes a rounded
forebody followed by a straight afterbody.
The assembly may further include an axially or downstream extending injector
cooling
flowpath disposed in the pilot housing and radially between a fuel nozzle
inner casing and
the centerbody. An upstream forward end of the centerbody includes an annular
chamfered leading edge of the forward end and a radially inwardly facing
conical
chamfered surface of the chamfered leading edge.
The assembly may further include substantially concentric primary and
secondary pilot
fuel nozzles in the pilot fuel injector tip and a main fuel nozzle spaced
radially outwardly
of the primary and secondary pilot fuel nozzles. The primary and secondary
pilot fuel
nozzles include circular primary and annular secondary exits respectively and
the circular
primary exit is located axially aftwardly and downstream of the annular
secondary exit.
The assembly may further include an annular secondary fuel supply passage
operable for
flowing fuel to the annular secondary exit in the secondary pilot fuel nozzle
and an
annular secondary fuel swirler in the secondary fuel supply passage. The
secondary fuel
swirler includes an annular array of helical spin slots which may have
rectangular cross
sections.
The pilot nose cap may include a rounded forebody followed by a straight
afterbody. The
rounded forebody includes a substantially rounded dome extending axially
forwardly or
upstream from a rounded nose base. The straight afterbody includes a
substantially
cylindrical nose afterbody extending axially aftwardly or downstream from the
nose base
and parallel to a pilot nose centerline perpendicular or normal to the nose
base. The pilot
nose centerline may be collinear or angled with respect to the centerline
axis.
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The dome may be a generally oval rounded dome with the nose base including a
generally
oval perimeter. The nose base may further include a generally oval perimeter
including
circular first and second end segments connected by spaced apart side
segments.
One exemplary embodiment of the dome includes circular first and second end
segments
being mirror image arcs having first radii. The side segments being generally
mirror
image arcs having second radii substantially greater than the first radii.
Straight middle
sections being centered in the side segments. The dome may further include a
center
conical section extending forwardly or upstream from the straight middle
sections. The
nose afterbody includes spaced apart rounded first and second ends
corresponding to and
extending aftwardly or downstream from the circular first and second end
segments. The
nose afterbody includes spaced apart generally curved sides corresponding to
and
extending aftwardly or downstream from the curved side segments. The nose
afterbody
includes a rectangular middle section disposed between the rounded first and
second ends
and the rectangular middle section includes spaced apart flat sides
corresponding to and
extending aftwardly or downstream from the straight middle sections.
One exemplary embodiment of the arm fairing includes rounded leading and
trailing
edges, a rectangular middle section extending therebetween, and the
rectangular middle
section including generally flat and generally circumferentially spaced apart
flat first and
second sides.
One exemplary embodiment of the pilot fuel injector tip includes substantially
concentric
primary and secondary pilot fuel nozzles, primary and secondary fuel supply
passages of
the primary and secondary pilot fuel nozzles respectively, and primary and
secondary fuel
transfer tubes connected to the primary and secondary fuel supply passages
respectively.
BRIEF DESCRIPTION OF THE DRAWINGS
The foregoing aspects and other features of the invention are explained in the
following
description, taken in connection with the accompanying drawings where:
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FIG. 1 is a cross-sectional view illustration of a gas turbine engine
combustor with an
exemplary embodiment of an aerodynamically enhanced fuel nozzle with main and
dual
orifice pilot nozzles.
FIG. 2 is an enlarged cross-sectional view illustration of the fuel nozzle
illustrated in FIG.
1.
FIG. 3 is a cross-sectional view illustration of a cross over arm in the fuel
injector taken
through 3-3 in FIG. 2.
FIG. 4 is an axial perspective view illustration of the fuel nozzle
illustrated in FIG. 2.
FIG. 5 is a longitudinal sectional view illustration of fuel nozzle
illustrated in FIG. 2.
FIG. 6 is a longitudinal sectional view illustration of an exemplary
embodiment of a dual
orifice pilot fuel injector tip having substantially concentric primary and
secondary pilot
fuel nozzles in the fuel nozzle illustrated in FIG. 2.
FIG. 7 is cut-away perspective view illustration of the dual orifice pilot
fuel injector tip
illustrated in FIG. 2 with helical fuel swirling slots in the secondary pilot
fuel nozzle.
FIG. 8 is a perspective view diagrammatic illustration of a pilot nose cap of
the pilot fuel
injector tip of the fuel nozzle illustrated in FIG. 2.
DETAILED DESCRIPTION OF THE INVENTION
Illustrated in FIG. 1 is an exemplary embodiment of a combustor 16 including a
combustion zone 18 defined between and by annular radially outer and inner
liners 20,
22, respectively circumscribed about an engine centerline 52. The outer and
inner liners
20, 22 are located radially inwardly of an annular combustor casing 26 which
extends
circumferentially around outer and inner liners 20, 22. The combustor 16 also
includes an
annular dome 34 mounted upstream of the combustion zone 18 and attached to the
outer
and inner liners 20, 22. The dome 34 defines an upstream end 36 of the
combustion zone
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18 and a plurality of mixer assemblies 40 (only one is illustrated) are spaced
circumferentially around the dome 34. Each mixer assembly 40 includes a main
mixer
104 mounted in the dome 34 and a pilot mixer 102.
The combustor 16 receives an annular stream of pressurized compressor
discharge air 14
from a high pressure compressor discharge outlet 69 at what is referred to as
CDP air
(compressor discharge pressure air). A first portion 23 of the compressor
discharge air 14
flows into the mixer assembly 40, where fuel is also injected to mix with the
air and form
a fuel-air mixture 65 that is provided to the combustion zone 18 for
combustion. Ignition
of the fuel-air mixture 65 is accomplished by a suitable igniter 70, and the
resulting
combustion gases 60 flow in an axial direction toward and into an annular,
first stage
turbine nozzle 72. The first stage turbine nozzle 72 is defined by an annular
flow channel
that includes a plurality of radially extending, circularly-spaced nozzle
vanes 74 that turn
the gases so that they flow angularly and impinge upon the first stage turbine
blades (not
shown) of a first turbine (not shown).
The arrows in FIG. 1 illustrate the directions in which compressor discharge
air flows
within combustor 16. A second portion 24 of the compressor discharge air 14
flows
around the outer liner 20 and a third portion 25 of the compressor discharge
air 14 flows
around the inner liner 22. A fuel injector 10, further illustrated in FIG. 2,
includes a
nozzle mount or flange 30 adapted to be fixed and sealed to the combustor
casing 26. A
hollow stem 32 of the fuel injector 10 is integral with or fixed to the flange
30 (such as by
brazing or welding) and includes a fuel nozzle assembly 12. The hollow stem 32
supports the fuel nozzle assembly 12 and the pilot mixer 102. A valve housing
37 at the
top of the stem 32 contains valves illustrated and discussed in more detail in
United
States Patent Application No. 20100263382, referenced above.
Referring to FIG. 2, the fuel nozzle assembly 12 includes a main fuel nozzle
61 and an
annular pilot inlet 54 to the pilot mixer 102 through which the first portion
23 of the
compressor discharge air 14 flows. The fuel nozzle assembly 12 further
includes a dual
orifice pilot fuel injector tip 57 substantially centered in the annular pilot
inlet 54. The
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dual orifice pilot fuel injector tip 57 includes concentric primary and
secondary pilot fuel
nozzles 58, 59. The pilot mixer 102 includes a centerline axis 120 about which
the dual
orifice pilot fuel injector tip 57, the primary and secondary pilot fuel
nozzles 58, 59, the
annular pilot inlet 54 and the main fuel nozzle 61 are centered and
circumscribed.
The main fuel nozzle 61 is spaced radially outwardly of the primary and
secondary pilot
fuel nozzles 58, 59. The secondary pilot fuel nozzle 59 is radially located
directly
adjacent to and surrounds the primary pilot fuel nozzle 58. The primary and
secondary
pilot fuel nozzles 58, 59 and main fuel nozzle 61 and the mixer assembly 40
are used to
deliver the fuel air mixture 65 to the combustion zone 18. The main fuel
nozzle 61
includes a circular or annular array of radially outwardly open fuel injection
orifices 63.
A fuel nozzle outer casing 71 surrounds the main fuel nozzle 61 and includes
cylindrical
fuel spray holes 73 aligned with the fuel injection orifices 63.
A pilot housing 99 includes a centerbody 103 and radially inwardly supports
the pilot fuel
injector tip 57 and radially outwardly supports the main fuel nozzle 61. The
centerbody
103 is radially disposed between the pilot fuel injector tip 57 and the main
fuel nozzle 61.
The centerbody 103 surrounds the pilot mixer 102 and defines a chamber 105
that is in
flow communication with, and downstream from, the pilot mixer 102. The pilot
mixer
102 radially supports the dual orifice pilot fuel injector tip 57 at a
radially inner diameter
ID and the centerbody 103 radially supports the main fuel nozzle 61 at a
radially outer
diameter OD with respect to the engine centerline 52. The main fuel nozzle 61
is
disposed within the main mixer 104 (illustrated in FIG. 1) of the mixer
assembly 40 and
the dual orifice pilot fuel injector tip 57 is disposed within the pilot mixer
102.
The pilot mixer 102 includes an inner pilot swirler 112 located radially
outwardly of and
adjacent to the dual orifice pilot fuel injector tip 57, an outer pilot
swirler 114 located
radially outwardly of the inner pilot swirler 112, and a swirler splitter 116
positioned
therebetween. The swirler splitter 116 extends downstream of the dual orifice
pilot fuel
injector tip 57 and a venturi 118 is formed in a downstream portion 115 of the
swirler
splitter 116. The venturi 118 includes a converging section 117, a diverging
section 119,
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and a throat 121 therebetween. The throat 121 is located downstream of a
primary exit 98
of the primary pilot fuel nozzle 58. The inner and outer pilot swirlers 112,
114 are
generally oriented parallel to the centerline axis 120 of the dual orifice
pilot fuel injector
tip 57 and the mixing assembly 40. The inner and outer pilot swirlers 112, 114
include a
plurality of swirling vanes 44 for swirling air traveling therethrough. Fuel
and air are
provided to pilot mixer 102 at all times during the engine operating cycle so
that a
primary combustion zone 122 (illustrated in FIG. 1) is produced within a
central portion
of combustion zone 18.
The primary and secondary pilot fuel nozzles 58, 59 have circular primary and
annular
secondary exits 98, 100 respectively, are operable to inject fuel in a
generally downstream
direction, and are often referred to as a dual orifice nozzle. The main fuel
nozzle 61 is
operable to inject fuel in a generally radially outwardly direction through
the circular
array of radially outwardly open fuel injection orifices 63. The primary pilot
fuel nozzle
58 includes a primary fuel supply passage 158 which feeds fuel to the circular
primary
exit 98 at a first downstream end 142 of the primary pilot fuel nozzle 58. The
secondary
pilot fuel nozzle 59 includes an annular secondary fuel supply passage 159
which flows
fuel to the annular secondary exit 100 at a second downstream end 143 of the
secondary
pilot fuel nozzle 59.
Referring to FIGS. 2 and 5-7, a primary fuel swirler 136 adjacent the
downstream end 142
of the primary fuel supply passage 158 is used to swirl the fuel flow exiting
the circular
primary exit 98. The exemplary primary fuel swirler 136 illustrated herein is
a cylindrical
plug having downstream and circumferentially angled fuel injection holes 164
to pre-film
a conical primary exit orifice 166 of the primary pilot fuel nozzle 58 with
fuel which
improves atomization of the fuel. The conical primary exit orifice 166
culminates at the
circular primary exit 98. The primary fuel swirler 136 swirls the fuel and
centrifugal
force of the swirling fuel forces the fuel against a primary conical surface
168 of the
conical primary exit orifice 166 thus pre-filming the fuel along the primary
conical
surface 168.
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Referring to FIGS. 2 and 5-7, an annular secondary fuel swirler 137 in the
annular
secondary fuel supply passage 159 adjacent the downstream end 143 of the
secondary
pilot fuel nozzle 59 is used to swirl the fuel flow exiting the annular
secondary exit 100.
The exemplary secondary fuel swirler 137, as illustrated herein, is an annular
array 180 of
helical spin slots 182 operable to pre-film a conical secondary exit orifice
167 of the
secondary pilot fuel nozzle 59 with fuel which improves atomization of the
fuel. The
helical spin slots 182 are illustrated herein as having a rectangular cross
section 183 with
respect to fuel flow direction through the helical spin slots 182. The conical
secondary
exit orifice 167 culminates at the annular secondary exit 100. The secondary
fuel swirler
137 swirls the fuel and centrifugal force of the swirling fuel forces it
against a secondary
conical surface 169 of the conical secondary exit orifice 167 thus pre-filming
the fuel
along the secondary conical surface 169.
Concentric annular primary and secondary fuel films from the concentric
primary and
secondary pilot fuel nozzles 58, 59 respectively merge together and the
combined fuel is
atomized by an air stream from the pilot mixer 102 which is at its maximum
velocity in a
plane in the vicinity of the annular secondary exit 100. In order to reduce
interaction
between the primary and secondary fuel films ejected from the concentric
primary and
secondary pilot fuel nozzles 58, 59, the circular primary exit 98 is located
axially aft and
downstream of the annular secondary exit 100. This results in physically
separating the
primary and secondary fuel films after they are ejected from the concentric
primary and
secondary pilot fuel nozzles 58, 59.
This separation better positions the fuel films within a shear layer of inner
pilot swirler
flow 138 from the inner pilot swirler 112 and improves fuel atomization and
reduces
intermittency in the overall spray quality over a wide-range of engine
operating
conditions. This also allows an accurate placement of fuel close to the shear
layers to
provide maximum flexibility which in turn plays a major role in emissions and
engine
operability over a range of engine operating conditions. Locating the circular
primary
exit 98 axially aft and downstream of the annular secondary exit 100 allows
the pre-
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filming primary conical surface 168 of the conical primary exit orifice 166 of
the primary
pilot fuel nozzle 58 and the secondary conical surface 169 of the conical
secondary exit
orifice 167 of the secondary pilot fuel nozzle 59 to release fuel closest to
the incoming
shear layer and do so consistently for a variety of fueling modes and engine
operating
conditions.
Referring to FIGS. 5 and 6, the inner pilot swirler 112 has a generally
cylindrical inner
pilot swirler flowpath section 222 followed by an annular inwardly tapering
conical
flowpath section 224 between the swirler splitter 116 and a radially outer
wall 226 of the
pilot fuel injector tip 57. The conical flowpath section 224 surrounds the
first
downstream end 142 of the primary pilot fuel nozzle 58 including the circular
primary
exit 98. The conical flowpath section 224 also surrounds secondary the second
downstream end 143 of the secondary pilot fuel nozzle 59 including the annular
secondary exit 100.
The inwardly tapering conical flowpath section 224 is radially inwardly
bounded by an
inwardly tapering conical wall section 230 of the radially outer wall 226 in
the converging
section 117 of the venturi 118. Illustrated in FIG. 6 is a conical surface 232
in space
defined by the inwardly tapering conical wall section 230. The circular
primary and
annular secondary exits 98, 100 may be axially located substantially up to but
not axially
aft or downstream of the conical surface 232 in order to release fuel closest
to the
incoming shear layer and do so consistently for a variety of fueling modes and
engine
operating conditions.
A cross over arm 56, illustrated in FIGS. 2, 3, and 4, extends radially across
the annular
pilot inlet 54 from the main fuel nozzle 61 to the pilot fuel injector tip 57.
The cross over
arm 56 includes an aerodynamically drag reducing cross over arm fairing 62, or
tube,
surrounding primary and secondary fuel transfer tubes 64, 66 used to transfer
fuel across
the annular pilot inlet 54 to the primary and secondary fuel supply passages
158, 159
respectively in the pilot fuel injector tip 57. The cross over arm fairing 62
includes
rounded leading and trailing edges 80, 82 and generally flat and generally
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circumferentially spaced apart flat first and second sides 67, 68 defining a
rectangular
middle section 76 extending between the rounded leading and trailing edges 80,
82. The
rounded leading and trailing edges 80, 82 illustrated herein are semi-
cylindrical. The
rounded leading edge 80 is representative of a rounded forebody 46 and the
rectangular
middle section 76 with the spaced apart flat first and second sides 67, 68 is
representative
of a straight afterbody 48.
Referring to FIGS. 1-5 and 8, an aerodynamically drag reducing pilot nose cap
53 also
referred to as a bullet nose or rounded nose is located at an upstream end 55
of the pilot
fuel injector tip 57. The pilot nose cap 53 includes a rounded or more
specifically a
generally oval shaped nose base 77 and a substantially rounded dome 78
extending
forwardly or upstream from the nose base 77. A cylindrical nose afterbody 92
or more
specifically a substantially oval cylindrical nose afterbody 92 extends
axially aft or
downstream from the nose base 77. The nose afterbody 92 is centered about and
parallel
to a pilot nose centerline 111 perpendicular or normal to the nose base 77.
The rounded
dome 78 is representative of a rounded forebody 46 and the nose afterbody 92
is
representative of a straight afterbody 48.
The pilot nose centerline 111 is illustrated herein as collinear with the
centerline axis 120
about which the pilot fuel injector tip 57 is centered and circumscribed.
Alternatively, the
pilot nose centerline 111 may be angled and/or slightly offset with respect to
the
centerline axis 120 to more evenly distribute and align pilot airflow 101
flowing into the
pilot mixer 102 and its inner and outer pilot swirlers 112, 114. The pilot
nose centerline
111 may be angled up to about 10 degrees with respect to the centerline axis
120.
As illustrated herein, the pilot nose cap 53 includes a generally oval shaped
nose base 77
and a substantially rounded dome 78 extending forwardly or upstream from the
nose base
77. The dome 78 is illustrated herein as a generally oval rounded dome having
a slight
blunted or flat top 86. The nose base 77 has a generally oval perimeter 88
with circular
first and second end segments 106, 108 connected by spaced apart substantially
curved
side segments 109. The circular first and second end segments 106, 108 are
mirror image
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arcs having first radii R1. The exemplary curved side segments 109 are
illustrated herein
as being generally mirror image arcs having second radii R2 substantially
greater than the
first radii R1. The exemplary curved side segments 109 illustrated herein also
include
straight middle sections 113 centered in the curved side segments 109. A
center conical
section 90 of the dome 78 extends forwardly or upstream from the straight
middle
sections 113 of the curved side segments 109 and illustrated herein as having
a
rectangular flat top 86.
The nose afterbody 92 is illustrated as having oval cross sectional shape
matching the
oval perimeter 88 of the nose base 77. The nose afterbody 92 extends aft or
downstream
from and at substantially 90 degrees from or normal to the nose base 77. The
nose
afterbody 92 includes spaced apart rounded first and second ends 146, 148
corresponding
to the circular first and second end segments 106, 108. The nose afterbody 92
further
includes spaced apart generally curved sides 409 corresponding to the curved
side
segments 109 of the oval perimeter 88. The exemplary embodiment of the nose
afterbody
92 illustrated herein also includes a rectangular middle section 149 disposed
between the
rounded first and second ends 146, 148. The rectangular middle section 149
includes
spaced apart flat sides 152 corresponding to the straight middle sections 113
of the oval
perimeter 88. The curved and flat sides 409, 152 extend aft or downstream from
the
curved side segments 109 and straight middle sections 113 respectively of the
oval
perimeter 88.
The cross over arm fairing 62 and the pilot nose cap 53 are both example of
fuel injector
fairings designed to minimize flow obstruction, avoid asymmetric flow, and
maximize the
pilot airflow 101 through the pilot mixer 102 and its inner and outer pilot
swirlers 112,
114. The fuel injector fairings are designed to promote pilot flame
stabilization by
increasing pilot inner swirl number and improve pilot atomization by
increasing pilot air
velocity of the pilot airflow 101. The cross over arm fairing 62 and the pilot
nose cap 53
have rounded forebodies 46 followed by straight afterbodies 48. The exemplary
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embodiment of the fuel nozzle assembly 12 illustrated herein depicts the
straight
afterbodies 48 as being parallel to the pilot nose centerline 111.
Referring to FIGS. 2 and 5, an axially or downstream extending injector
cooling flowpath
190 is disposed in the pilot housing 99 and radially between a fuel nozzle
inner casing 79
and the centerbody 103. The main fuel nozzle 61 is radially disposed outwardly
of and
supported at least in part by the fuel nozzle inner casing 79. The injector
cooling
flowpath 190 extends axially downstream or aft from the annular pilot inlet 54
to an aft
annular plenum 192 at an aft end 194 of the injector cooling flowpath 190. The
aft
annular plenum 192 includes an annular groove, slot, or pocket 195 in a
radially
outwardly extending aft flange 196 of the fuel nozzle inner casing 79 and is
radially
inwardly bounded by the centerbody 103. Cooling holes 198 through an axially
aft
annular wall 200 of the aft flange 196 direct cooling air from the aft annular
plenum 192
onto a radially outwardly extending aft heat shield flange 197 on an aft end
202 of the
centerbody 103. An annular heat shield 204 faces the combustion zone 18 and is
mounted on the heat shield flange 197.
An annular cooling flowpath inlet 206 to the injector cooling flowpath 190 is
radially
inwardly bounded by the centerbody 103. An upstream forward end 208 of the
centerbody 103 is radially disposed between the outer pilot swirler 114 and
the
centerbody 103 and operates as a flow splitter between the outer pilot swirler
114 and the
annular cooling flowpath inlet 206 to the injector cooling flowpath 190. The
forward end
208 of the centerbody 103 is an annular wall section including an annular
chamfered
leading edge 210 having a radially inwardly facing conical chamfered surface
212. The
chamfered leading edge 210 operates as a dirt deflector that diverts dirt in
the pilot
airflow 101 away from the cooling flowpath inlet 206.
The present invention has been described in an illustrative manner. It is to
be understood
that the terminology which has been used is intended to be in the nature of
words of
description rather than of limitation. While there have been described herein,
what are
considered to be preferred and exemplary embodiments of the present invention,
other
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modifications of the invention shall be apparent to those skilled in the art
from the
teachings herein and, it is, therefore, desired to be secured in the appended
claims all such
modifications as fall within the true spirit and scope of the invention.
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